June, 1920] FORESTRY 293 



pice stands of southern France by 2, 3, and even 1 years. This delay in:ty be a blessing in 

 disguise since it affords an opportunity to lengthen the rotation with the object of producing 

 larger sized material, which iii the last ir> or 20 years has become increasingly valuable. 

 Assuming that the Vesulian law (that the volume produd ion varies as I be square of the age) 

 holds for trees between 20 and 30 years old, calculations indicate that the net revenue will 

 be three or four times as great at 25 as at 20 years of age. The longei rotal i o is also prefer- 

 able from a silvicultural point of view since the short rotations commonly in use have impov- 

 erished both soil and stands. — S. T. Dana. 



2012. Dk la Hamelinate, H. De l'utilite et de la tenue des calepins de balivage. [Use- 

 fulness and preservation of staddle notebooks.] Rev. Eaux et Forets 57:200-201. 1919.— 

 Staddle notebooks should always be preserved since they often contain much information of 

 the greatest value, particularly when they cover two or three rotations. The only difficulty 

 in using them lies in the fact that the classifications used, which should always be clearly 

 noted in the notebooks themselves, have varied from time to time. This is particularly 

 serious when the staddle has not been regarded as limited to seedlings of the same age as the 

 coppice, but as including all seedlings of a given size irrespective of their age. This prac- 

 tice, which is now becoming common, is open to serious objection, since it frequently leads to 

 inability on the part of forest officers to determine to which rotation a given tree belongs. 

 The result is that when it is necessary to choose between retaining a young standard of the 

 same rotation as the coppice and another of the previous rotation, the latter is usually 

 chosen in spite of the fact that its future growth will be decidedly less. — S. T. Dana. 



2013. De Jong, A. W. K. Tapproeven bij Hevea brasiliensis. [Tapping experiments on 

 Hevea brasiliensis.] Arch. Rubbercult. Nederlandsch. Indie 3: 1-6. 1919. — Results of 5§ 

 years of tapping experiments: One left cut 1.60 m. high on a third tapped twice daily gives 

 less latex than other systems of tapping. One left cut 1.10 m. high on a quarter tapped 

 twuce daily and three left cuts at a distance of 50 cm. on a quarter tapped twice daily give 

 less than the following three methods: Two left cuts on a quarter at a distance of 50 cm. 

 tapped daily, two left cuts on a third at a distance of 75 cm. tapped daily, and two left cuts 

 on a third beginning at 85 cm. height, one going upward and the other as usual, tapped 

 daily. The last three methods give practically the same yield. One left cut on each of 

 two opposite quarters at 1.10 m. height tapped daily gives 30 per cent more rubber than the 

 three last mentioned. Results of 18 months experiments show tapping from left to right has 

 an advantage in yield of 14 per cent over similar tapping from right to left. — W. E. Cake. 



2014. De Vries, O. Invloed van enkele chemicalien op de innerlijke eigenschappen van 

 den rubber. [Influence of certain chemicals on the inner qualities of rubber.] Arch. Rub- 

 bercult. Nederlandsch. Indie. 2:67-104. 1918. — A review of experiments with some of the 

 chemicals most commonly used in the preparation of rubber from Hevea latex, viz: anti- 

 coagulants, sodium sulphite, formaldehyde, and sodium carbonate; anti-oxydants, sodium 

 bisulphite and thiosulphate; the closely related substances, sodium acetate and sulphurous 

 acid. Sodium sulphite is placed in the front rank as an anti-coagulant by the fact that it 

 causes a small but decided improvement of the rubber in tensile strength, a diminution of the 

 standard time of cure and of the slope of the stress-strain curve, and an increase in viscosity 

 index. Formaldehyde has just the opposite effect. Sodium carbonate has little effect. 

 The effects of sodium bisulphite on the rubber are good. Thiosulphate in general has negli- 

 gible effects. In making the usual types of plantation rubber, crepe and smoked sheet, 

 acetic acid is used as a coagulant. In the case of three of the substances examined, sodium 

 sulphite, bisulphite, and thiosulphate, interaction with acetic acid yields two common reac- 

 tion products, sodium acetate and sulphurous acid. Sodium acetate increases rate of cure 

 and viscosity; improvement in tensile strength and viscosity, if actual, .are very small. 

 Sulphurous acid, as a coagulant, has a favorable influence on the inner qualities of the rub- 

 ber, as compared with acetic acid, and shows a small increase in tensile strength and vis- 

 cosity, a marked decrease in slope of the stress-strain curve, whilst the rate of cure remains 



